Woodlice evolved from marine isopods which are presumed to have colonised land in the Carboniferous, though the oldest known fossils are from the Cretaceous period.

Woodlice have many common names and although often referred to as terrestrial isopods, some species live semiterrestrially or have recolonised aquatic environments like those of the genus Ligia.

Woodlice have a basic morphology of a segmented, dorso-ventrally flattened body with seven pairs of jointed legs, and specialised appendages for respiration.

Like other peracarids, female woodlice carry fertilised eggs in their marsupium, through which they provide developing embryos with water, oxygen and nutrients.

[6] Key adaptations to terrestrial life have led to a highly diverse set of animals; from the marine littoral zone and subterranean lakes to arid deserts and desert slopes 4,725 m (15,500 ft) above sea-level, woodlice have established themselves in most terrestrial biomes and represent the full range of transitional forms and behaviours for living on land.

They are popular as terrarium pets because of their varied colour and texture forms, conglobating ability and ease of care.

A number of common names make reference to the fact that some species of woodlice can roll up into a ball.

A female woodlouse will keep fertilised eggs in a marsupium on the underside of her body, which covers the under surface of the thorax and is formed by overlapping plates attached to the bases of the first five pairs of legs.

[40] Some woodlouse species, like Armadillidium maculatum, seem to display Batesian Mimicry to certain pill millipedes like Glomeris marginata.Many members of Oniscidea live in terrestrial, non-aquatic environments, breathing through trachea-like lungs in their paddle-shaped hind legs (pleopods), called pleopodal lungs.

Evolutionary ancient species are amphibious, such as the marine-intertidal sea slater (Ligia oceanica), which belongs to family Ligiidae.

Species for which aquatic life is assumed include Typhlotricholigoides aquaticus (Mexico) and Cantabroniscus primitivus (Spain).

[4] Although woodlice, like earthworms, are generally considered beneficial in gardens for their role in controlling certain pests,[47] producing compost and overturning the soil, some species like those of the genus Armadillidium have also been known to feed on cultivated plants, such as ripening strawberries and tender seedlings.

[52] While some isopod species are kept purely as pets, some can also be used as an addition to bioactive terrariums, due to their ability to break down decaying organic materials.

Some isopod morphs are characterized by polygenic traits, such as 'Orange Vigor' (Armadillidium vulgare) and 'Pink Rubber Ducky' (Cubaris sp.

T− albino isopods are thought to lack both melanin and tyrosinase, and therefore only express light yellows, oranges, and white.